Problem: Solve for $x$ and $y$ using substitution. ${-3x-4y = -2}$ ${x = 2y+4}$
Since $x$ has already been solved for, substitute $2y+4$ for $x$ in the first equation. ${-3}{(2y+4)}{- 4y = -2}$ Simplify and solve for $y$ $-6y-12 - 4y = -2$ $-10y-12 = -2$ $-10y-12{+12} = -2{+12}$ $-10y = 10$ $\dfrac{-10y}{{-10}} = \dfrac{10}{{-10}}$ ${y = -1}$ Now that you know ${y = -1}$ , plug it back into $\thinspace {x = 2y+4}\thinspace$ to find $x$ ${x = 2}{(-1)}{ + 4}$ $x = -2 + 4$ ${x = 2}$ You can also plug ${y = -1}$ into $\thinspace {-3x-4y = -2}\thinspace$ and get the same answer for $x$ : ${-3x - 4}{(-1)}{= -2}$ ${x = 2}$